But 10 minutes after that first, unheralded entrance, Bloom breaks into hysterics – and so does the audience at “The Producers.”

Two years and several cast changes later, Mel Brooks’ ode to audacity is still, Huns down, the funniest show in town.

The old ladies are still dancing with their walkers, the pigeons are still saluting and “Springtime for Hitler” is as over-the-top as ever.

Only now it’s Bart – a bigger nebbish than Broderick or Weber – who plays Bloom, lacing his tissue-thin tenor with an encyclopedic repertoire of squeals, tremors and tics culled from a lifetime of watching Daffy Duck cartoons.

Eagle-eyed observers will recognize him from his pre-Bloom days, when he played Carmen Ghia, the swishy assistant to flamboyant director Roger DeBris. Together, they were one of the cutest couples on Broadway.

As Leo, Bart gets the girl: Cady Huffman, whose statuesque Ulla seems to loom over Bart’s fragile little Bloom, and looks as if she can polish him off with her breakfast herring.

“We’re both 5-foot-9,” Huffman says. “I just look bigger.”

Sniffling slightly and wearing a wool cap, the 40-year-old father of two – a 16-year-old and the 22-month-old he helped deliver the day “The Producers” opened in Chicago – looked a lot like Snoopy, the role that won him a Tony.

Even with a raging head cold, it’s clear he loves being Leo.

“I get to sing love songs and dance with a beautiful actress,” he marvels.

“The daunting part about it is, as Carmen I was on about 18 minutes and now I’m on for an hour and 45 minutes.

“Maybe I’ll get my dancer butt back.”

Cast changes haven’t gone smoothly for the show that, in its Nathan Lane-Matthew Broderick prime, commanded $480 a ticket.

After they left, the producers of “The Producers” decided to bring in what Bart calls “two new guys, who could learn the show together and maybe strike up a rapport.”

The new guys turned out to be Weber and Henry Goodman, the Max who was axed because he wasn’t funny. In came Brad Oscar, Lane’s understudy when he wasn’t playing the crazed Nazi playwright Franz Liebkind.

Both the cast and critics loved him – but they weren’t wild about Weber.

“Mostly, he registers as a handsome, conventional leading man impersonating a nerd,” wrote Ben Brantley in the Times, while The Post’s Clive Barnes missed Broderick’s “queasy, collapsible innocence.”

Nevertheless, Weber managed to hang onto his job until his contract ran out in mid-December.